Research in this laboratory is directed towards an understanding of the mechanism of light and dark-adaptation in Limulus ventral photoreceptors and other invertebtate photoreceptors that may be of particular interest. We will look into the possibility that plasma-membrane rhodopsin sends a chemical transmitter to an intracellular store, causing it to release calcium, and thereby producing light-adaptation. The approach will consist of injecting intracellularly possible candidates and assaying their effect on excitation and adaptation. In addition we will begiF an investigation of the parolfactory vesicles of squid. These photoreceptors may prove ideal for simultaneous electrophysiological recording and spectral measurements of visual pigment.